Abstract:
In Thailand, 98.5% of the imported x-ray films are used for medical services. After the developing process, approximately 55-56% of metallic silver still remains on the developed x-ray films. The used films are practically kept at the hospitals for record-keeping purposes for 5-10 years, while the developing agents are resued at minimal twice. The discarded films and the spent (fixer_ solution are normally sold to waste dealers. Wastes are delivered to in-house factories to recover silver by electrolysis, acid leaching (HNO ) or combustion processes. The dealer for used x-ray waste is one of the major stakeholders who is apparently exempted from state control and regulations. Depending on its size and capacity, the processors must have a factory-operating permit. Most unlicensed processors have no concern about the handling of their wastes. Highly toxic chemicals are generally spilled and discharged into the environment. The cleaner technology concept of silver leaching from processed radiographic film was investigated using weak organic acids such as acetic, oxalic, and malonic acids. The tests were carried out under different temperature conditions. An oxalic acid solution at 5% (w/v) provided the best leaching conditions at 100 C, 20-minute retention time and at 90 C, 60 minute-retention time to achieve >97% SRE (Silver Recovery Efficiency). The reclaimed silver was in its metal form and ready for ingot transformation. Following this, a fact sheet on the waste management of radiographic film waste was developed to initiate and support the need to reduce the risks of contamination of hazardous silver into the environment.
